The present invention relates to step exercising machines, and relates more particularly to such a step exercising machine which forces the pedals to oscillate leftwards and rightwards alternatively, when the pedals are peddled up and down.
FIGS. 4 and 5 show a step exercising machine according to the prior art. This structure of step exercising machine comprises a base 1' having an upright post 11' and a horizontally disposed arched rack 12', a hollow revolving shaft 4' sleeved onto the upright post 11', bearing 44' mounted on the revolving shaft 4' at the top, a top transverse rod 41' and a bottom transverse rod 42' fixedly fastened to the periphery of the revolving shaft 4' at the back side at different elevations, a horizontal gear holder 43' perpendicularly connected to the revolving shaft 4' at the front side to hold a sprocket wheel 5' and a sector gear 51', permitting the sector gear 51' to be maintained in engagement with the rack 12', two pedals 2' adapted for pedaling, and two hydraulic cylinders 3' adapted for providing a damping force to the pedals 2'. Each pedal has a barrel 21 ' at the rear end coupled to one end of the top transverse rod 41', a downward coupling plate 22' disposed below the barrel 21' and coupled to one end of the bottom transverse rod 42', and a bottom ring 23' near the front end. Each hydraulic cylinder 3' has a coupling ring 32' at the rear end of the casing thereof coupled to one end of the bottom transverse rod 42', and a piston rod 31 ' with an eyed end 33' pivoted to the bottom ring 23' of one pedal 2'. Furthermore, a chain 6' is mounted on the sprocket wheel 5', having two opposite ends respectively connected to the downward coupling plates 22' of the pedals 2'; and upright frame 7' may be fastened to the upright post 4' to hold a handlebar 71'. When the pedals are peddled, the revolving shaft is forced to turn forwards and backwards alternatively, thereby causing the pedals to oscillate leftwards and rightwards alternatively. However, this structure of step exercising machine has drawbacks. One drawback of this structure of step exercising machine is that high noises will be produced when the chain and the sector gear are respectively moved relative to the sprocket wheel and the rack. Another drawback of this structure of step exercising machine is that the chain tends to disengage from the sprocket wheel during the operation of the step exercising machine. Furthermore, this structure of step exercising machine is complicated, therefore its manufacturing cost is high.